1. Field of the Invention
The present invention relates to a catalyst converter device for purifying exhaust gas in which a catalyst retainer obtained by a catalyst is carried by a carrier and retained inside a metal tubular member through a retaining mat. A saddle-ride type vehicle includes the catalyst converter device for purifying exhaust gas.
2. Description of Background Art
In an exhaust system of an engine, a catalyst converter device is provided that includes a catalyst that purifies hydrocarbon, carbon monoxide and nitrogen oxide included in exhaust gas.
As such a catalyst converter device, there is one wherein a catalyst retainer obtained by a catalyst is carried by a carrier and retained through a retaining mat inside a metal tubular member provided in an exhaust pipe or a muffler. In addition, the catalyst retainer is retained by interference of the retaining mat inserted between the catalyst retainer and the metal tubular member.
A retaining mat is known that is included in the catalyst converter device and is formed of two layers of an alumina fiber layer and a ceramic fiber layer. See, for example, JP-A No. 2004-204819. A method is known for assembling a catalyst converter device by winding a retaining mat around a catalyst retainer using an organic sheet and thereafter pressing-in the catalyst retainer to a metal tubular member. See, for example, Japanese Patent No. 3527966.
In JP-A No. 2004-204819, after one layer out of two layers is formed, another layer is formed on the layer to form an integrated sheet. However, the man-hour for production is increased as compared to forming a retaining mat of a single layer, and productivity drops. In addition, in Japanese Patent No. 3527966, because an organic sheet is wound outside a retaining mat, a drop of productivity becomes a problem due to an increase in the production process.
In such a case of making the retaining mat of two layers and using an organic sheet in addition to a retaining mat as described above, because the clearance between the catalyst retainer and the metal tubular member for inserting the retaining mat reduces, in order to be able to obtain a predetermined interference of the retaining mat, if the inside diameter of the metal tubular member is the same, the outside diameter of the catalyst retainer should be made small.
If the outside diameter of the catalyst retainer is made small, the surface area of the catalyst reduces, and flow path resistance of an exhaust gas flow passage increases. Thereby, exhaust gas purification performance and engine performance are affected.